The disclosure of the present application relates generally to clamps, and more particularly, to homeostatic tissue clamps.
Evidence has shown that the mechanical stresses and strains in the cardiovascular system are under strict regulation, i.e., there exists a homeostatic range of mechanical stresses and strains in the cardiovascular system. These stresses may include homeostatic circumferential stress due to pressure, and axial stress due to axial pre-stretch. A perturbation of the mechanical loading (i.e., change in blood pressure or vessel length) leads to biochemical and biological responses, and these responses may lead to vascular dysfunction including atherosclerosis.
Numerous studies have quantified the degree of longitudinal shortening when a blood vessel is excised from the in situ condition. Computational models have shown that the effect of axial pre-stretch is to increase circumferential and longitudinal stresses. Interestingly, experimental studies have shown that longitudinal retraction or pre-stretch is small in early stages of life and increases with postnatal growth and development as the vessels are stretched by bodily growth. The net effect of these computational and experimental observations indicate that a more similar magnitude of circumferential and longitudinal stresses (homeostasis) may be obtained by pre-stretching the vessel to in vivo levels.
These observations have important implications as a change in blood pressure (hypertension or hypotension) or axial stretch lead to growth and remodeling. In addition to the chronic effects, it is known that removal of vessel and hence axial retraction and circumferential decompression (zero pressure) may cause damage to the endothelium and reduction of nitric oxide (NO). Since NO is atheroprotective, this induces a risk for cell adhesion and thrombosis. In the surgical practice of vessel grafting, the free graft is typically allowed to retract axially and deflate circumferentially which may promote acute vasospasm or thrombosis. Furthermore, the graft is not pre-stretched to the natural in vivo level after implantation which may promote vascular remodeling and stenosis.
Thus, there is a need in the art for a clamping device and a technique of maintaining the natural stress and strain conditions of a tissue that is to be manipulated. The clamping device should be easy to understand and use, universally adoptable, efficient and relatively inexpensive.